<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style> 
        .box{
            display: grid;
            grid-template-columns: 1fr 1fr 1fr 1fr;
            grid-template-rows: 1fr 1fr 1fr;
            background-color: aqua;
            gap: 10px;
            padding: 10px;
        }
        .box div{
            background-color: aliceblue;
            text-align: center;
            font-size: 30px;
        }
        .box .a1{
            grid-column-start: 1;
            grid-column-end: 5;
        }
        .box .a2{
            grid-row-start: 2;
            grid-row-end: 4;
        }
        .box .a3{
            grid-column-start: 2;
            grid-column-end: 4;
        }
        .box .a5{
            grid-column-start: 2;
            grid-column-end: 5;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="a1">头部</div>
        <div class="a2">菜单</div>
        <div class="a3">主要内容区域</div>
        <div class="a4">右侧</div>
        <div class="a5">底部</div>
    </div>
</body>
</html>